The present invention relates to an aortic shunt apparatus and methods for cerebral embolic protection by isolating the aortic arch vessels from the aortic lumen, selectively perfusing the arch vessels with a fluid and directing blood flow within the aortic lumen and any potential embolic materials carried in the blood through a shunt past the isolated arch vessels.
The perfusion shunt apparatus of the present invention may be mounted on a catheter or cannula for percutaneous introduction or for direct insertion into a circulatory vessel, such as the aorta. The perfusion shunt apparatus has application for protecting a patient from embolic stroke or hypoperfusion during cardiopulmonary bypass or cardiac surgery and also for selectively perfusing the cerebrovascular circulation with oxygenated blood or with neuroprotective fluids in the presence of risk factors, such as head trauma or cardiac insufficiency. The perfusion shunt apparatus will also find application for selective perfusion of other organ systems within the body.
Over the past decades tremendous advances have been made in the area of heart surgery, including such life saving surgical procedures as coronary artery bypass grafting (CABG) and cardiac valve repair or replacement surgery. Cardiopulmonary bypass (CPB) is an important enabling technology that has helped to make these advances possible. Recently, however, there has been a growing awareness within the medical community and among the patient population of the potential sequelae or adverse affects of heart surgery and of cardiopulmonary bypass. Chief among these concerns is the potential for stroke or neurologic deficit associated with heart surgery and with cardiopulmonary bypass. One of the likely causes of stroke and of neurologic deficit is the release of emboli into the blood stream during heart surgery. Potential embolic materials include atherosclerotic plaques or calcific plaques from within the ascending aorta or cardiac valves and thrombus or clots from within the chambers of the heart. These potential emboli may be dislodged during surgical manipulation of the heart and the ascending aorta or due to high velocity jetting (sometimes called the xe2x80x9csandblasting effectxe2x80x9d) from the aortic perfusion cannula. Air that enters the heart chambers or the blood stream during surgery through open incisions or through the aortic perfusion cannula is another source of potential emboli. Emboli that lodge in the brain may cause a stroke or other neurologic deficit. Clinical studies have shown a correlation between the number and size of emboli passing through the carotid arteries and the frequency and severity of neurologic damage. At least one study has found that frank strokes seem to be associated with macroemboli larger than approximately 100 micrometers in size, whereas more subtle neurologic deficits seem to be associated with multiple microemboli smaller than approximately 100 micrometers in size. In order to improve the outcome of cardiac surgery and to avoid adverse neurological effects it would be very beneficial to eliminate or reduce the potential of such cerebral embolic events.
Several medical journal articles have been published relating to cerebral embolization and adverse cerebral outcomes associated with cardiac surgery, e.g.: Determination or Size of Aortic Emboli and Embolic Load During Coronary Artery Bypass Grafting; Barbut et al.; Ann Thorac Surg 1997; 63; 1262-7; Aortic Atheromatosis and Risks of Cerebral Embolization; Barbut et al.; J Card and Vasc Anesth, Vol 10, No 1, 1996; pp 24-30; Aortic Atheroma is Related to Outcome but not Numbers of Emboli During Coronary Bypass; Barbut et al.; Ann Thorac Surg 1997; 64; 454-9; Adverse Cerebral Outcomes After Coronary Artery Bypass Surgery; Roach et al.; New England J of Med, Vol 335, No 25, 1996; pp 1857-1863; Signs of Brain Cell Injury During Open Heart Operations; Past and Present; .ANG.berg; Ann Thorac Surg 1995; 59; 1312-5; The Role of CPB Management in Neurobehavioral Outcomes After Cardiac Surgery; Murkin; Ann Thorac Surg 1995; 59; 1308-11; Risk Factors for Cerebral Injury and Cardiac Surgery; Mills; Ann Thorac Surg 1995; 59; 1296-9; Brain Microemboli Associated with Cardiopulmonary Bypass; A Histologic and Magnetic Resonance Imaging Study; Moody et al.; Ann Thorac Surg 1995; 59; 1304-7; CNS Dysfunction After Cardiac Surgery; Defining the Problem; Murkin; Ann Thorac Surg 1995; 59; 1287+; Statement of Consensus on Assessment of Neurobehavioral Outcomes After Cardiac Surgery; Murkin et al.; Ann Thorac Surg 1995; 59; 1289-95; Heart-Brain Interactions; Neurocardiology Comes of Age; Sherman et al.; Mayo Clin Proc 62: 1158-1160, 1987; Cerebral Hemodynamics After Low-Flow Versus No-Flow Procedures; van der Linden; Ann Thorac Surg 1995; 59; 1321-5; Predictors of Cognitive Decline After Cardiac Operation; Newman et al.; Ann Thorac Surg 1995; 59; 1326-30; Cardiopulmonary Bypass; Perioperative Cerebral Blood Flow and Postoperative Cognitive Deficit; Venn et al.; Ann Thorac Surg 1995; 59; 1331-5; Long-Term Neurologic Outcome After Cardiac Operations; Sotaniemi; Ann Thorac Surg 1995; 59; 1336-9; Macroemboli and Microemboli During Cardiopulmonary Bypass; Blauth; Ann Thorac Surg 1995; 59; 1300-3.
Commonly owned, co-pending U.S. provision application No. 60/060,117, and corresponding U.S. patent application Ser. No. 09/158,405, which are hereby incorporated by reference, describe an aortic perfusion filter catheter for prevention of cerebral embolization and embolic stroke during cardiopulmonary bypass or cardiac surgery. The patent literature also includes several other references relating to vascular filter devices for reducing or eliminating the potential of embolization. These and all other patents and patent applications referred to herein are hereby incorporated by reference in their entirety. The following U.S. patents relates to vena cava filters; U.S. Pat. Nos. 5,549,626, 5,415,630, 5,152,777, 5,375,612, 4,793,348, 4,817,600, 4,969,891, 5,059,205, 5,324,304, 5,108,418, 4,494,531. The following U.S. patents relate to vascular filter devices: U.S. Pat. Nos. 5,496,277, 5,108,419, 4,723,549, 3,996,938. The following U.S. patents relate to aortic filters or aortic filters associated with atherectomy devices: U.S. Pat. Nos. 5,662,671, 5,769,816. The following international patent applications relate to aortic filters or aortic filters associated with atherectomy devices: WO 97/17100, WO 97/42879, WO 98/02084. The following international patent application relates to a carotid artery filter; WO 98/24377. The patent literature also includes the following U.S. patents related to vascular shunts and associated catheters: U.S. Pat. Nos. 3,991,767, 5,129,883, 5,613,948. None of these patents related to vascular shunts provides an apparatus or method suitable for preventing of cerebral embolization and embolic stroke or for performing selective perfusion of the aortic arch vessels to prevent hypoperfusion during cardiopulmonary bypass or cardiac surgery.
While some of these previous devices and systems represent advances in the prevention of some causes of neurologic damage, there continues to be a tremendous need for improved apparatus and methods to prevent cerebral embolization, embolic stroke and cerebral hypoperfusion during cardiopulmonary bypass and cardiac surgery. Similarly, there continues to be a tremendous need for apparatus and methods for selective perfusion of the cerebrovascular circulation with oxygenated blood or with neuroprotective fluids in the presence of risk factors, such as head trauma or cardiac insufficiency and also for selective perfusion of other organ systems within the body.
In keeping with the foregoing discussion, the present invention takes the form of a perfusion shunt apparatus and methods for isolating and selectively perfusing a segment of a patient""s cardiovascular system and for directing circulatory flow around the isolated segment. In a particularly preferred embodiment of the invention, the perfusion shunt apparatus is configured as an aortic perfusion shunt apparatus for deployment within a patient""s aortic arch and methods are described for isolating the aortic arch vessels from the aortic lumen, for selectively perfusing the arch vessels with a fluid and for directing blood flow within the aortic lumen through a shunt conduit past the isolated arch vessels. The perfusion shunt apparatus may be mounted on a catheter or cannula for percutaneous introduction via peripheral artery access or for direct insertion into a circulatory vessel, such as the aorta. The perfusion shunt apparatus protects the patient from cerebral embolization and embolic stroke during cardiopulmonary bypass or cardiac surgery by directing potential emboli downstream from the aortic arch vessels where they will be better tolerated by the body. The perfusion shunt apparatus further protects the patient from cerebral hypoperfusion by providing selective perfusion of the aortic arch vessels and the cerebrovascular circulation with oxygenated blood or with neuroprotective fluids. The perfusion shunt apparatus also finds application for selective perfusion of the cerebrovascular circulation in the presence of risk factors, such as head trauma or cardiac insufficiency. The perfusion shunt apparatus will also find application for selective perfusion of other organ systems within the body.
The perfusion shunt apparatus of the present invention includes an expandable shunt conduit with an upstream end, a downstream end and an internal lumen. The expandable shunt conduit is mounted on a catheter or cannula for percutaneous introduction via peripheral artery access or for direct insertion into the aorta. The expandable shunt conduit is a generally cylindrical tube of a flexible polymeric material or fabric that may be impermeable or porous to blood. Located at the upstream end of the expandable shunt conduit is an upstream sealing member. A downstream sealing member is located at the downstream end of the expandable shunt conduit. Optionally, the expandable shunt conduit may also include a plurality of support members that bridge between the upstream sealing member and the downstream sealing member. When deployed, the upstream sealing member and the downstream sealing member support the expandable shunt conduit in an open, deployed configuration and create a seal between the expandable shunt conduit and the vessel wall. An annular chamber is created between the vessel wall and the shunt conduit. A perfusion lumen within the catheter shaft communicates with the annular chamber external to the shunt conduit.
In one particularly preferred embodiment, the upstream sealing member and the downstream sealing member are inflatable toroidal balloon cuffs, which are sealingly attached to the upstream end and the downstream end of the expandable shunt conduit. In another embodiment, the upstream sealing member and the downstream sealing member are in the form of selectively deployable external flow valves. In yet another embodiment, the upstream sealing member and the downstream sealing member include extendible and retractable elongated expansion members to expand the upstream and downstream ends of the expandable shunt conduit until they contact and create a seal against the inner surface of the aorta.
Optionally, an outer tube may be provided to cover the shunt conduit when it is in the collapsed state in order to create a smooth outer surface for insertion and withdrawal of the perfusion shunt apparatus and to prevent premature deployment of the shunt conduit. Optionally, each embodiment of the perfusion shunt apparatus may also include an occlusion device, such as an inflatable balloon, to selectively occlude and seal the lumen of the expandable shunt conduit. Each embodiment of the perfusion shunt apparatus may also include an embolic filter for filtering potential emboli from the blood passing through the internal lumen of the expandable shunt conduit. Each embodiment of the perfusion shunt apparatus may include one or more radiopaque markers, sonoreflective markers or light emitting devices to enhance imaging of the apparatus using fluoroscopy, ultrasonic imaging or aortic transillumination.